A recently released large-scale Danish study looked at any possible risk for autism from the MMR vaccine and the conclusion was that "MMR vaccination does not increase the risk for autism, does not trigger autism in susceptible children, and is not associated with clustering of autism cases after vaccination".
The emergency declaration follows a previously announced Department of Health exclusion order barring unvaccinated children from attending schools and day cares within both Williamsburg and Borough Park, and demonstrates a shift in the city's focus to combating the disease in the northern Brooklyn neighborhood, where the majority of new measles cases have been discovered, according to de Blasio. As of Monday, there were single reports of people infected in Wayne and Washtenaw counties.
Of those infected, 246 were children, NY health commissioner Oxiris Barbot said.
Health officials have largely blamed the outbreaks on small but vocal anti-vaccine advocates who scare well-meaning parents by spreading unsafe lies and misinformation about life-saving vaccines and their safety.
Measles is highly contagious, spreading through coughs and sneezes. The cases led to 21 hospitalizations, including five admissions to intensive care units. All but 39 of the confirmed cases are in children.
He said some parents refuse vaccines because they're concerned about short-term side effects, such as pain from the injection or a fever.
Deliberately exposing a child to chickenpox comes with risks.
Exposing kids to measles is even more unsafe.
The Brooklyn outbreak has been traced to an unvaccinated child who became infected on a visit to Israel, which is also grappling with an outbreak, according to New York City's Department of Health.
Officials said they would help people arrange to get shots but were prepared to fine them as much as $1,000 if they refused.
The measles vaccine, which the CDC recommends children get two doses of, is 97 percent effective, according to health officials. 'The schools are cooperating, everyone's cooperating'.
He said he had seen misinformation circulate around the tightly knit community, but that most families trusted the Health Department.
That's the point of vaccines - safe ways of making people immune to infections with limited side effects.
Schlesinger is working with the Orthodox community to reverse the spread of false messaging.
"There is a very strong anti-vaccination propaganda movement in these communities, and they're very effective", said Blima Marcus, a nurse practitioner who lives in Brooklyn.
"This is the epicentre of a measles outbreak that is very, very troubling and must be dealt with immediately", de Blasio said.
The city can't legally physically force someone to get a vaccination, but officials said people who ignore the order could be fined $1,000 (£767).
Neighborhood officials said the vast majority of Orthodox Jews in Williamsburg are vaccinated, but because the community is so tightly knit, just a small number of anti-vaxers is allowing this outbreak to grow.